This invention relates to hospital beds. Such beds are usually provided with devices for raising and lowering the patient and for permitting pivotal movement of the patient's upper body portion towards a sitting position as well as upward pivotal movement of his thighs. To accomplish these functions, most hospital beds are provided with a base support frame, a primary frame mounted upon the base frame and a mattress frame. Often, the primary frame supports electric motors and drive mechanisms for vertically moving the primary frame relative to the base frame and for pivoting the head and thigh sections of the mattress frame. Thus, three separate frames have been found desirable to accomplish the desired functions.
Hospital beds employing these three horizontal frames present some disadvantages. These primarily include difficulties in maneuverability due to length and weight, higher cost in terms of additional fabrication and assembly, and a complicated power lift linkage mechanism.